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Post subject: I castrated my Twin today...
Posted: Sat Nov 03, 2012 5:17 pm
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I decided to take some of the oomph out of my TRRI today... I haven't needed it for gigging for years, and just about the time I think it's sounding sweet in my jam room, it's loud enough to start peeling paint off the walls. I have been toying with the idea of trading it in on an early 70's Pro Reverb but there are so many of these TRRI's floating around that I didn't think I'd get much for it, either in trade or in a straight sale.

I was also curious about modding to be able to toggle it down to 25 watts... which seemed like a cool option until I explored it and found out how expensive it would be to have done, and it's certainly not something I'd tackle myself.

But, in my poking around, I discovered what apparently many have known for a long time, that you can disconnect a speaker and remove the two outside power tubes and basically "half-power" your twin with no further to-do. So now it's essentially a 40 watt amp with 1 12" speaker... I just got done with it and it sounds great. It's still loud as all get out (albeit not as loud) and clean as can be, but I can turn up the volume just that much more to get a richness out of it than I was able to before. Not to mention that I was able to roll up the bass a bit...with some of my guitars, I actually have to turn it all the way down but now I've got it up in the 4/5 range... it's sounds fantastic! I was pretty stoked to find a free and easy mod to tame down the Twin. Of course, now I'm tempted to upgrade the speaker knowing that I don't need to purchase two of them! I've always thought I'd like to try a Tone Tubby.

Just curious, has anyone else done this to their Twin before?


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Post subject: Re: I castrated my Twin today...
Posted: Sat Nov 03, 2012 9:07 pm
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It's commonly known that you can pull two of the four output tubes on most amps to reduce output power, which also creates an impedance mismatch, further limiting output power. Disconnecting one speaker creates an impedance mismatch that, by itself, will lower the output power, and both changes might affect the tone somewhat. Nice discovery. :)

Really, you can achieve the same thing by simply turning the volume down. :o

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Post subject: Re: I castrated my Twin today...
Posted: Sat Nov 03, 2012 11:18 pm
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Quote:
Really, you can achieve the same thing by simply turning the volume down.


This is true, but for playing at home it's hard to get the twin's volume higher than 2/3. I don't think the amp sounds great until the volume is at least at 3, and 4 sounded much better but it was just too loud. Now, I can comfortably play at around 4 and it sounds great. I haven't noticed much in the way of a tonal change, though there does seem to be more note separation.

I was reading a few articles where Steve Kimock was discussing his preference of playing amps with two, instead of four, output tubes. He feels that something is lost with four output tubes, and the added output of 4 power tubes seems to accentuate this mainly because all it adds is more volume. I don't really understand the science of it all but to my ears, and apparently his, it sounds better. I simply don't need an 85 watt amp and even though 45 watts is still way more than I probably need, it's more suited to playing at home. It's still clean as can be with all the headroom I'll ever need, the characteristics that make the twin so desirable IMO.Even with my lengthy pedal chain it sounds good.

In any event, I'm happy with how it sounds and it doesn't seem like it will mess the amp up in any way which was a primary concern. And, if I decide to switch it back, it's as simple as hooking up the other speaker and putting the tubes back.


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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 4:57 am
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Best is to use a good attenuator. Removing 2 tubes and /or one speaker don't lower enough db.


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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 5:53 am
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My Hot Rod Deluxe is loud as hell. Could you do this on that without harming it? It's a 1 X 12 so I don't have the option of disconnecting a speaker.

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 6:25 am
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lenrabinowitz wrote:
My Hot Rod Deluxe is loud as hell. Could you do this on that without harming it? It's a 1 X 12 so I don't have the option of disconnecting a speaker.



No. Your amp should have 2 pairs of output tube. HotRod Deluxe , IMO have only 1 pair ;

Attenuator is the answer.


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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 6:50 am
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stratele52 is correct, one pair of output tubes in the HRDlx.

However, you can create an impedance mismatch by inserting a dummy plug into the external speaker jack while leaving the internal speaker plugged into its jack. This will lower the output power because you will have an 8 ohm speaker connected to the 4 ohm tap of the OT. Also, plug the guitar into input 2 as it is attenuated and you will have less volume than when using input 1. You might affect the tone of the amp by doing this, but no harm in trying it.

Effectively what the OP did was create an impedance mismatch by removing two output tubes, but then re-matched the impedance by disconnecting one of the two speakers, still lowering the output power by roughly half. Basically, turning the volume pot down would achieve the same thing, but if it sounds better to him.......OK, it's possible that the sound was slightly different.

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 6:59 am
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I'm a little confused but I think I get it.

It has two output tubes. I guess that is "1 pair."

If I understand you both, I cannot go down to one output tube?

Forgot about the second input- That is worth trying. Might try the dummy speaker connector also.

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 7:01 am
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What is a "dummy plug" exactly- Plug in a speaker cable with no speaker attached?

Thanks!

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 7:30 am
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A plug that dropped out of school. :lol:

It is just the phone plug itself, with not even a cable attached to it. Use the empty plug into the external speaker jack, activating a built-in switch in that jack, which switches to the 4 ohm tap on the OT.

Image

lenrabinowitz wrote:
...If I understand you both, I cannot go down to one output tube?...


I have heard amps with only one of the two output tubes working, and surprisingly the amp can produce sound. Although I'm not completely sure, it's almost certainly not good for the amp to run with only one of the two output tubes.

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 7:43 am
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shimmilou wrote:
A plug that dropped out of school. :lol:

It is just the phone plug itself, with not even a cable attached to it. Use the empty plug into the external speaker jack, activating a built-in switch in that jack, which switches to the 4 ohm tap on the OT.

Image

lenrabinowitz wrote:
...If I understand you both, I cannot go down to one output tube?...


I have heard amps with only one of the two output tubes working, and surprisingly the amp can produce sound. Although I'm not completely sure, it's almost certainly not good for the amp to run with only one of the two output tubes.


Would this be considered also on a VK ?

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 7:56 am
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Not the same for the VK, it has only one tap on the OT, and the external speaker jack has no switch. For the VK, plug in an external speaker along with the internal for an impedance mismatch, but that's a different ballgame as you now have an extra speaker connected. You can change the speakers connected to the amp, using different impedance speakers. A good practice for a tube amp is to keep the impedance mismatch to a 2 to 1 ratio, either high or low. I usually find that half of the speaker impedance sounds better than twice the speaker impedance. Sometimes, but not always, a matched impedance sounds best.

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 8:32 am
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there
Quote:
Best is to use a good attenuator. Removing 2 tubes and /or one speaker don't lower enough db.


As noted in my earlier posts, the difference in volume/output is not dramatic, but it does exist. It makes enough of a difference that I'm happy with the outcome and have no plans to change it back... best of all it was FREE.

So please correct me if I'm wrong, but could I then reattach the other speaker and use one of those dummy plugs in my speaker out to achieve the same thing as disconnecting as speaker as I've done now? I think I'm happy with it as-is... though as I mentioned, I'm tempted now to go to a single speaker... perhaps making a new baffle for a 15", and shedding some weight by using a Weber Neomag. They're supposed to more or less capture the tone of the old JBL's... very intriguing 8)


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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 9:47 am
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JamGuy wrote:
and shedding some weight by using a Weber Neomag. They're supposed to more or less capture the tone of the old JBL's... very intriguing 8)


Absolute and unequivocal bullshit.

Arjay

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Post subject: Re: I castrated my Twin today...
Posted: Sun Nov 04, 2012 9:53 am
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Another way to lower the final volume & not get too much compression --- is change the gain stage tubes from 12AX7 to 5751 or even 12AY7. Do this to the input tube(s) first. As this stage nearly always has the greatest gain in Fender amps.


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